An RDF is a HDF with an RDB. You cannot have real bad blocks in any type of image format. These images only store user data, 512 bytes per block. There is no way to make such a block bad (unreadable). A real harddrive stores error detection data on the magnetic disk so that it can determine whether the user data is still intact or not. The data in an image file is always intact, there is no way to store a bad block in an image file.

Then the RDB part of an RDF cannot strictly conform to the RigidDiskBlock specification given in the Amiga ROM Kernel Reference Manual, and my thoughts above about how the nature of the bad block mapping and replacement would render an RDF quite useless as a testcase for bad block handling of a proposed Disk Monitor application are therefore invalid.

Nevertheless, what you have written above confirms that an RDF won't, in any event, provide the testcase that the OP is seeking.